1. Field of the Invention
The present invention relates to a BLU (Back Light Unit) module, and particularly relates to a thin-type BLU module with effective heat dissipation and high uniform luminance.
2. Background of the Invention
A BLU is a device providing a backlight source that is usually placed behind a panel of an information, a communication or a consumer product, such as an LCD (Liquid Crystal Display), a film scanner, an optical lantern, and so on. In particular, the BLU is widely used in LCDs, which is thin, lightweight, and portable, and occupies a certain degree of the display market share. As LCD technology develops, the tendency is towards large and cheap units, and the BLU needs to be light weight, thin, power conservative, brightly lit, and cheap, simultaneously. For success in the competitive market, new designs of the BLU, new technologies of the injection molding process, and the like should be constructive issues to the industry.
Generally speaking, a conventional BLU can be classified into two categories in terms of locations of light sources therein, such as edge lighting and bottom lighting. In the first category, an edge lighting BLU 1a, referring to FIG. 1, is suitable in small-size liquid crystal module 9a and light guide 10a, which are usually under 14 inches. There are two major types of light sources 11a in the edge lighting BLU, whether single sided or double sided, a CCFL (Cold Cathode Fluorescent Lamp) and an LED (Light Emitting Diode), which is thinner, lighter, and more power conservative than that with the CCFL and usually used in a notebook. The edge lighting BLU 1a further includes a diffusion sheet 13a and a prism sheet 14a arranged over the light guide 10a for increasing the uniformity and the symmetry thereof, and a reflection sheet 12a disposed beneath the light guide 10a for raising the luminance thereof. In the second category, a bottom lighting BLU 2a, referring to FIG. 2, is suitable in a large LCD that is usually over 17 inches, in which size the edge lighting BLU 1a is unwelcome because it make the unit heavy, dark and power consumptive. Thus, the bottom lighting BLU 2a is provided, and light sources 21a consisting of a plurality of CCFLs are distributed behind a display screen for direct view via a reflection sheet 22a under the light sources 21a and a light guide (or a diffusion sheet) 20a over the light sources 21a. The bottom lighting BLU 2a provides a lightweight, bright and large LCD, with a large view angle with a simple structure and high lighting efficiency, and usually used in a monitor. A prism sheet 23 is applicable over the light guide (or the diffusion sheet) 20a for a larger view angle. However, this conventional unit has several drawbacks. First, the large light guide (or diffusion sheet) 20a is extremely difficult to manufacture in the injection molding process and requires and expensive mold. Second, the CCFLs of the light sources 21a use a lot of power and make the shape of the lamp configuration visible, which in turn causes a non-homogeneous illumination thereof. Third, the CCFLs of the light sources 21a make heat dissipation very troublesome, and addition of a heat sink module sacrifices the thinness and weight thereof. Fourth, the CCFLs of the light sources 21a include noxious chemicals, like mercury, and should be replaced by another type of lighting.
Hence, an improvement over the prior art is required to overcome the disadvantages thereof.